In a semiconductor rectifying device that rectifies an input current to output the rectified current, there are a Pin diode having a pn junction and a Schottky barrier diode (SBD) having a carrier potential barrier of a difference in work function between a semiconductor layer and metal. In the Schottky barrier diode, there is a JBS (Junction Barrier Schottky barrier diode) in which an impurity region (for example, p type) having a conductive type different from that of the semiconductor layer (for example, n type) is disposed at a surface of the semiconductor layer in order to relax an electric field applied to an interface between the semiconductor layer and the metal. There is also an MPS (Merged PiN-diode Schottky-diode). In the MPS, the contact between the impurity region (for example, p type) and the metal of the JBS is set to or brought close to ohmic connection, and a minority carrier is injected to decrease a resistance by conductivity modulation when a voltage exceeding a built-in potential (Vbi) between the impurity region and the semiconductor layer.
On the other hand, a wide bandgap semiconductor such as silicon carbide (hereinafter also referred to as SiC) is expected as a next-generation power semiconductor device. The wide bandgap semiconductor has a wide bandgap, higher breakdown field strength, and higher thermal conductivity compared with Si Silicon). A low power-loss power semiconductor device operable at high temperature can be realized utilizing the characteristics of the wide bandgap semiconductor.
In the MPS, by decreasing a voltage at which conductivity modulation is generated, a low resistance of a forward characteristic is realized, and a large amount of current can be ejected at a low forward voltage when a forward surge current flows. When a current larger than that of a steady state flows, the current causes a crystal breakdown and a junction breakdown due to heat generation under an equation of current×voltage=energy. However, when the large amount of current is passed at the low forward voltage, heat generation energy can be suppressed to decrease an device destruction ratio.
For the SiC diode in which the conductivity modulation is generated by a minority carrier, a Stacking Fault (SF) that is a plane defect is generated by energy of electron/hole plasma recombination while originating on a Basal Plain Dislocation (BPD) propagating from an SiC substrate to an epitaxial layer, thereby degrading the forward characteristic. That is, when the stacking fault is generated, the carrier is trapped to decrease an on-state current of the diode.